1. Field of the Invention
The present invention relates to a non-reciprocal circuit device, particularly a non-reciprocal circuit device, such as an isolator, a circulator or the like, used in a microwave band, and a radio communication terminal device.
2. Description of the Related Art
A non-reciprocal circuit device, such as an isolator, a circulator or the like has a characteristic of transmitting a signal in only a specified direction and of not transmitting a signal in the opposite direction. Based on such a characteristic, for example, a circulator is used in a transmitting and receiving circuit of a mobile communication device such as a cell phone.
In this type of circulator, a plurality of central conductors are arranged on a main surface of a magnetic core (ferrite core), and a DC field is applied to the ferrite core from a permanent magnet, thereby coupling the plurality of central conductors together. WO 00/59065 discloses that the passband of a circulator can be widened by providing a resonant circuit in addition to the central conductors. In recent years, however, various systems such as LTE are introduced to radio communication systems, and non-reciprocal circuit devices operable in a wider band are demanded to obtain simplified transmitting and receiving circuits.